This invention relates to packaging apparatus, and more particularly to apparatus for packaging a product in a tubular bag having its ends sealed closed.
Specifically, this invention relates to an improvement on packaging apparatus as disclosed in U.S. Pat. No. 2,976,657 to Cloud in which a product to be packaged is placed on a web, and the web is formed into a tube around the product and sealed and severed in front of and behind the product to form a bag. In the above-mentioned Cloud patent, the entubed products pass around a so-called rotary turret or wheel. A plurality of clamping assemblies or die sealing units are held stationary in a rest or hold position at one location on the wheel with the wheel rotating relative to the sealing units when the latter are in their hold position. In timed relation to movement of the portions of the tube between successive products therein, the sealing units are released one at a time from the hold position and are coupled to the wheel for being driven by the wheel. Each sealing unit has a fixed lower jaw and a hinged upper jaw swingable from an open to a closed position as the sealing unit moves from the hold position so as to clamp the tube between the jaws intermediate successive products in the tube. The jaws may be heated so as to heat-seal the tube, or may include other means to otherwise seal the tube transversely across the tube. Also, the jaws may carry a severing blade (or a heated wire) for severing the tube within the seal formed by the jaws thereby to form the trailing end seal of a leading bag and the leading end seal of a trailing bag. The jaws securely grip the web as the die moves with the wheel and thus pull the tube and products therein through the apparatus at the speed of the wheel.
As shown in the above-mentioned Cloud patent, the sealing units are released by an electric eye control system which senses the passage of registration marks preprinted at intervals on the web. This electric eye control system also actuates a so-called stop gate for controlling placement of the units to be packaged in spaced relation to the registration marks. Thus, the electric eye control system places the units to be packaged on the web in proper relation to the registration marks thereon and releases the sealing units in timed relation to movement of the registration marks so as to properly seal and sever the tube between successive units therein.
In other packaging apparatus generally similar to that shown in the above-mentioned U.S. Pat. No. 2,976,657, other means, such as another photoelectric control system, was provided for sensing the position of units to be packaged on the web and to effect coupling of a sealing unit to the wheel in timed releation to the movement of the units with the web. Thus, unprinted or clear web as well as printed web could be utilized to package units. However, if one or more of the units to be packaged was not placed on the web, this other photoelectric control system would not sense the presence of the units in the tube and thus would not release the sealing units. Hence, if several units in a row were not placed on the web and if sealing units were not released from the hold position, after a partial revolution of the wheel the sealing units would no longer be in gripping engagement with the web so as to pull it along its path through the apparatus. Furthermore, an excessive number of sealing units may accumulate at the hold position with possible damage to some of the sealing units. Thus, a limit switch actuable by the movement of the sealing units with the wheel was provided for releasing a sealing unit at some time after the next sealing unit should have been released by the above-mentioned other photoelectric control system. If, however, this other photoelectric control system functioned properly and released a sealing unit at the desired time, another limit switch actuable by the just-released sealing unit reset the first-mentioned limit switch and thus prevented it from releasing another die. In packaging units within a preprinted web, this first-mentioned limit switch was used to generate a signal to automatically position the units to be packaged on the web relative to registration marks preprinted on the web.
However, the above-mentioned limit switches, when adjusted for various package lengths, were found to interfere with the release of the sealing units and prevented access to certain parts of the apparatus. Also, adjustment of the position of the limit switches within the apparatus for accommodating various package lengths could not readily be accomplished by an operator from an operator's station.